FIG. 1 discloses an internal combustion engine and centrifugal separator assembly for separating contaminants in the form of liquid and/or solid particles from crankcase gas which is produced during operation of the engine. A crankcase of the engine is arranged to ventilate contaminated crankcase gas through the centrifugal separator. Hence, the crankcase is connected to a gas inlet of the centrifugal separator via a regulating valve which is arranged to maintain a desired gas pressure in the crankcase at different running conditions of the combustion engine (e.g. at different engine loads and/or speeds resulting in different amounts of crankcase gas being produced).
The gas inlet is configured to conduct crankcase gas, which is to be cleaned, to a central part of a centrifugal rotor. The centrifugal rotor comprises a plurality of separation discs for separating the particles from the crankcase gas, the centrifugal rotor being rotatably arranged in a separation space inside a rotor housing. The cleaned crankcase gas is discharged from the rotor housing through a gas outlet, which is configured to communicate with a part of the separation space surrounding the centrifugal rotor.
The particles in the crankcase gas are separated by the separation discs and thrown from the centrifugal rotor onto an inside wall of the rotor housing. A particle outlet communicates with the part of the separation space surrounding the centrifugal rotor, wherein the separated particles will flow down along the inside wall and out of the separation space via the particle outlet. The separated particles are thereafter conducted to the crankcase of the engine.
The shown system is configured as a so called closed crankcase ventilation system. Accordingly, the cleaned crankcase gas from the gas outlet of the centrifugal separator is connected to an air intake of the engine. The gas outlet is connected to the air intake downstream of an air filter and upstream of a compressor of a turbocharger.
During normal operation of the engine and the centrifugal separator, the gas pressure in the separation space surrounding the centrifugal rotor is higher than the pressure in the crankcase. Such a pressure difference is desirable, because it promotes the flow of separated particles out of the particle outlet to the crankcase of the engine. A small fraction of the cleaned crankcase gas may flow through the particle outlet to the crankcase, which improves the drainage by drawing the separated particles out of the particle outlet and into the crankcase.
There is a risk however that the pressure in the separation space surrounding the centrifugal rotor becomes lower than the pressure in the crankcase. This could for instance be due to a pressure drop over the air intake filter, and/or a pressure drop over the regulating valve between the crankcase and the centrifugal separator. This results in an undesired pressure difference, between the separation space and the crankcase, which counteracts or prevents the flow of separated particles to the crankcase. It may even cause an undesired flow of crankcase gas to the centrifugal separator via the particle outlet. The improper drainage of separated particles will eventually lead to contamination of the cleaned gas inside the separation space surrounding the centrifugal rotor.